Certain beverage preparation machines use capsules containing ingredients to be extracted or to be dissolved and/or ingredients that are stored and dosed automatically in the machine or else are added at the time of preparation of the drink. Some beverage machines possess filling means that include a pump for liquid, usually water, which pumps the liquid from a source of water that is cold or indeed heated through heating means, e.g. a thermoblock or the like. Especially in the field of coffee preparation, machines have been widely developed in which a capsule containing beverage ingredients is inserted in a brewing device. The brewing device is tightly closed about the capsule, water is injected at the first face of the capsule, the beverage is produced in the closed volume of the capsule and a brewed beverage can be drained from a second face of the capsule and collected into a receptacle such as a cup or glass.
Brewing devices have been developed to facilitate insertion of a “fresh” capsule and removal of the capsule upon use.
WO 2005/004683 and WO 2007/135136 relate to such brewing devices. The devices comprise a frame, a fixed holding part for the capsule, a movable holding part which is mounted relative to the frame in a sliding relationship, one or two knuckle joint mechanisms that provide a mechanical system which enables to close in a steady and fluid-tight manner the holding parts about the capsule while also resisting to the counter-force acting while re-opening and generated by the internal brewing pressure, and a handle for directly levering the knuckle joint mechanism. Such a device forms a simple assembly enabling insertion of the capsule by vertical fall through a passage in the frame and removal of the used capsule in the same direction as the insertion direction. The handle may serve to cover and uncover the passage for the capsule. The movable parts of the brewing device are actuated manually via the handle. The manual force required to move the movable parts varies during closure and opening of the machine and depends on the dimensional tolerances of the capsules used and the positioning and nature of the capsules as well as the temperature of the brewing unit. WO 2009/043630 discloses a beverage preparation machine including a brewing unit having a front part with a passage for inserting a capsule into the brewing unit. The front part is arranged to telescope out of the machine's housing for uncovering the passage for inserting a capsule into the brewing unit and telescopes into the brewing unit for sliding the passage under the housing and thus covering the passage by the housing. From a different approach, the actuation of the movable part of the brewing device may be motorized. EP 1 767 129 relates to a motor-driven extraction module for a capsule-based beverage production device. In this case, the user does not have to provide any manual effort to open or close the brewing device. WO 2012/025258 and WO 2012/025259 disclose other motorized machine for preparing beverages from ingredient capsules.
When the capsule containing the material to be extracted, e.g. a beverage ingredient, is partly or entirely sealed, in particular water and optionally air tight, it may be necessary to open the sealed capsule part by means of an appropriate opener. The opening may be delayed, i.e. during the extraction process of the capsule in the extraction unit e.g. as disclosed in EP 0 512 470 or in EP 2 068 684, or it may be carried out in the unit before extraction of the cartridge e.g. as disclosed in WO 02/00073 or in WO 02/35977. Further opening arrangements are disclosed in U.S. Pat. Nos. 3,260,190, 5,649,472, CH 605 293, EP 512 468 and EP 242 556.
An extraction unit may typically include one or more blades for forming an opening in a capsule before extraction of the capsule. When a blade is used which does not itself include a liquid circulation duct, i.e. a duct for guiding liquid into or out from the capsule, the liquid normally circulates, outside and along the blade, into or out from the capsule in a passage formed inbetween the blade the boundaries of the opening formed in the capsule by the blade in the capsule. The passage formed between the blade and these boundaries may be too small for allowing the desired flow of liquid into or out of the capsule. As a result, the flow along the capsule may be too small, or the capsule may be torn in an unwanted manner about the boundaries (in the case of a pressurized outflow of liquid from the capsule) or the capsule may be crushed (in the case of a pressurized inflow or attempted inflow of liquid into the capsule).
This problem has been addressed in WO02/00073. An extraction unit is disclosed which includes several capsule piercing blades that pierce a capsule for allowing a circulating of liquid through the capsule. The blades have transverse though-openings that extend into a cartridge during extraction to provide an increased space along the blade so as to facilitate introduction of liquid from outside into the cartridge.
The presence of such a through-opening across the blade improves significantly the flow of liquid into or out of the capsule by extending the section of the through-passage of liquid inwards in the blade about the boundaries of the opened capsule at the level of the blade. Such a through-opening however weakens the mechanical strength of the blade. This may become an issues over time, especially when harder capsules are used that are not easily pierced by the blade. Such an added constraint on the blade during piercing may of course lead to an early failure of the blade with the through-opening.